Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$200.59	4.435%	$209.4862	$209.49	$209.50	$209.50
Purchase #2	$102.44	8.735%	$111.3881	$111.39	$111.40	$111.40
Purchase #3	$195.63	5.395%	$206.1842	$206.18	$206.20	$206.20
Purchase #4	$70.70	11.517%	$78.8425	$78.84	$78.85	$78.80
Purchase #5	$238.37	5.444%	$251.3469	$251.35	$251.35	$251.30
Purchase #6	$212.79	7.303%	$228.3301	$228.33	$228.35	$228.30
Purchase #7	$110.98	3.143%	$114.4681	$114.47	$114.45	$114.50
7 purchase totals =	$1,131.50		$1,200.0461	$1,200.05	$1,200.10	$1,200.00